The Institute has been asked to confirm the
popular adage that the average person is
thermodynamically equivalent to a 100 watt
light bulb. The argument below indicates
that the only thing missing is the light
and the glass package.

100 Watts = 100 joules/second by definition.
Mr. Joule studied the heat produced while
boring cannon barrels and the international
unit of heat received his name. Continuing,
the energy produced or used per day if this
power level is sustained for 24 hours is:

100 watts = 100 j/s (x 86400 sec/day) = 8,640,000
j/day

A joule of energy is equivalent to 0.2388
calories. This is the standard thermodynamic
calorie roughly defined as the energy required
to raise the temperature of one gram of water
by one degree centigrade. So,

100 watts = 8,640,000 j/day = 2,063,233 calories/day.

This is probably the most confusing part:
a "food calorie" is actually 1000 standard
calories from thermodynamics, or a kilocalorie.
Apparently, the food guys have simply shortened
the proper kilocalorie to "calorie". Let's
call the kilocalorie the Kalorie to keep
them separate. Anyhow, you see that now we
have

100 watts = 2,063 Kalories/day

which is close to the food intake rate of
the average adult. This adult must radiate
this same power (on average), else he/she
would increase in temperature without limit.
During heavy work periods, the kaloric use
rate does increase above this to perhaps
double or triple the average. A fairly small
percentage of this goes to the actual work
being done but most of this is expended inside
the body because it is a very inefficient
machine. So, If one spends an hour at 200w,
the surface temperature rises (allowing more
heat to radiate from the skin and be cooled
convectively by air) and energy is stored
in the heat capacity of the body (mostly
water) to be dissipated by the body over
the next hour or so during rest.